package me.zk.practice1.s;

/**
 * @author zhangkai
 * @date 2023/7/13 11:53
 */
public class LS_Offer_25 {
    public static ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode node = new ListNode(-1);
        ListNode prev = node;
        while (l1 != null && l2 != null) {
            if (l1.val <= l2.val) {
                prev.next = l1;
                l1=l1.next;
            } else {
                prev.next = l2;
                l2 = l2.next;
            }
            prev = prev.next;
        }
        prev.next = l1 == null ? l2 : l1;
        return node.next;
    }
    public ListNode mergeTwoLists2(ListNode l1, ListNode l2) {
        ListNode prehead = new ListNode(-1);

        ListNode prev = prehead;
        while (l1 != null && l2 != null) {
            if (l1.val <= l2.val) {
                prev.next = l1;
                l1 = l1.next;
            } else {
                prev.next = l2;
                l2 = l2.next;
            }
            prev = prev.next;
        }

        // 合并后 l1 和 l2 最多只有一个还未被合并完，我们直接将链表末尾指向未合并完的链表即可
        prev.next = l1 == null ? l2 : l1;

        return prehead.next;
    }

    public static void main(String[] args) {
        ListNode l1 = new ListNode(1);
        ListNode n1 = new ListNode(2);
        l1.next = n1;
        ListNode n2 = new ListNode(4);
        n1.next = n2;

        ListNode l2 = new ListNode(1);
        ListNode n4 = new ListNode(3);
        l2.next = n4;
        ListNode n5 = new ListNode(4);
        n4.next = n5;
        mergeTwoLists(l1,l2);
    }
}
